"""Extract, format and print information about Python stack traces."""importlinecacheimportsysimporttypes__all__=['extract_stack','extract_tb','format_exception','format_exception_only','format_list','format_stack','format_tb','print_exc','format_exc','print_exception','print_last','print_stack','print_tb','tb_lineno']def_print(file,str='',terminator='\n'):file.write(str+terminator)defprint_list(extracted_list,file=None):"""Print the list of tuples as returned by extract_tb() or extract_stack() as a formatted stack trace to the given file."""iffileisNone:file=sys.stderrforfilename,lineno,name,lineinextracted_list:_print(file,' File "%s", line %d, in %s'%(filename,lineno,name))ifline:_print(file,' %s'%line.strip())defformat_list(extracted_list):"""Format a list of traceback entry tuples for printing. Given a list of tuples as returned by extract_tb() or extract_stack(), return a list of strings ready for printing. Each string in the resulting list corresponds to the item with the same index in the argument list. Each string ends in a newline; the strings may contain internal newlines as well, for those items whose source text line is not None. """list=[]forfilename,lineno,name,lineinextracted_list:item=' File "%s", line %d, in %s\n'%(filename,lineno,name)ifline:item=item+' %s\n'%line.strip()list.append(item)returnlistdefprint_tb(tb,limit=None,file=None):"""Print up to 'limit' stack trace entries from the traceback 'tb'. If 'limit' is omitted or None, all entries are printed. If 'file' is omitted or None, the output goes to sys.stderr; otherwise 'file' should be an open file or file-like object with a write() method. """iffileisNone:file=sys.stderriflimitisNone:ifhasattr(sys,'tracebacklimit'):limit=sys.tracebacklimitn=0whiletbisnotNoneand(limitisNoneorn<limit):f=tb.tb_framelineno=tb.tb_linenoco=f.f_codefilename=co.co_filenamename=co.co_name_print(file,' File "%s", line %d, in %s'%(filename,lineno,name))linecache.checkcache(filename)line=linecache.getline(filename,lineno,f.f_globals)ifline:_print(file,' '+line.strip())tb=tb.tb_nextn=n+1defformat_tb(tb,limit=None):"""A shorthand for 'format_list(extract_stack(f, limit))."""returnformat_list(extract_tb(tb,limit))defextract_tb(tb,limit=None):"""Return list of up to limit pre-processed entries from traceback. This is useful for alternate formatting of stack traces. If 'limit' is omitted or None, all entries are extracted. A pre-processed stack trace entry is a quadruple (filename, line number, function name, text) representing the information that is usually printed for a stack trace. The text is a string with leading and trailing whitespace stripped; if the source is not available it is None. """iflimitisNone:ifhasattr(sys,'tracebacklimit'):limit=sys.tracebacklimitlist=[]n=0whiletbisnotNoneand(limitisNoneorn<limit):f=tb.tb_framelineno=tb.tb_linenoco=f.f_codefilename=co.co_filenamename=co.co_namelinecache.checkcache(filename)line=linecache.getline(filename,lineno,f.f_globals)ifline:line=line.strip()else:line=Nonelist.append((filename,lineno,name,line))tb=tb.tb_nextn=n+1returnlistdefprint_exception(etype,value,tb,limit=None,file=None):"""Print exception up to 'limit' stack trace entries from 'tb' to 'file'. This differs from print_tb() in the following ways: (1) if traceback is not None, it prints a header "Traceback (most recent call last):"; (2) it prints the exception type and value after the stack trace; (3) if type is SyntaxError and value has the appropriate format, it prints the line where the syntax error occurred with a caret on the next line indicating the approximate position of the error. """iffileisNone:file=sys.stderriftb:_print(file,'Traceback (most recent call last):')print_tb(tb,limit,file)lines=format_exception_only(etype,value)forlineinlines[:-1]:_print(file,line,' ')_print(file,lines[-1],'')defformat_exception(etype,value,tb,limit=None):"""Format a stack trace and the exception information. The arguments have the same meaning as the corresponding arguments to print_exception(). The return value is a list of strings, each ending in a newline and some containing internal newlines. When these lines are concatenated and printed, exactly the same text is printed as does print_exception(). """iftb:list=['Traceback (most recent call last):\n']list=list+format_tb(tb,limit)else:list=[]list=list+format_exception_only(etype,value)returnlistdefformat_exception_only(etype,value):"""Format the exception part of a traceback. The arguments are the exception type and value such as given by sys.last_type and sys.last_value. The return value is a list of strings, each ending in a newline. Normally, the list contains a single string; however, for SyntaxError exceptions, it contains several lines that (when printed) display detailed information about where the syntax error occurred. The message indicating which exception occurred is always the last string in the list. """# An instance should not have a meaningful value parameter, but# sometimes does, particularly for string exceptions, such as# >>> raise string1, string2 # deprecated## Clear these out first because issubtype(string1, SyntaxError)# would throw another exception and mask the original problem.if(isinstance(etype,BaseException)orisinstance(etype,types.InstanceType)oretypeisNoneortype(etype)isstr):return[_format_final_exc_line(etype,value)]stype=etype.__name__ifnotissubclass(etype,SyntaxError):return[_format_final_exc_line(stype,value)]# It was a syntax error; show exactly where the problem was found.lines=[]try:msg,(filename,lineno,offset,badline)=valueexceptException:passelse:filename=filenameor"<string>"lines.append(' File "%s", line %d\n'%(filename,lineno))ifbadlineisnotNone:lines.append(' %s\n'%badline.strip())ifoffsetisnotNone:caretspace=badline[:offset].lstrip()# non-space whitespace (likes tabs) must be kept for alignmentcaretspace=((c.isspace()andcor' ')forcincaretspace)# only three spaces to account for offset1 == pos 0lines.append(' %s^\n'%''.join(caretspace))value=msglines.append(_format_final_exc_line(stype,value))returnlinesdef_format_final_exc_line(etype,value):"""Return a list of a single line -- normal case for format_exception_only"""valuestr=_some_str(value)ifvalueisNoneornotvaluestr:line="%s\n"%etypeelse:line="%s: %s\n"%(etype,valuestr)returnlinedef_some_str(value):try:returnstr(value)except:return'<unprintable %s object>'%type(value).__name__defprint_exc(limit=None,file=None):"""Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'. (In fact, it uses sys.exc_info() to retrieve the same information in a thread-safe way.)"""iffileisNone:file=sys.stderrtry:etype,value,tb=sys.exc_info()print_exception(etype,value,tb,limit,file)finally:etype=value=tb=Nonedefformat_exc(limit=None):"""Like print_exc() but return a string."""try:etype,value,tb=sys.exc_info()return''.join(format_exception(etype,value,tb,limit))finally:etype=value=tb=Nonedefprint_last(limit=None,file=None):"""This is a shorthand for 'print_exception(sys.last_type, sys.last_value, sys.last_traceback, limit, file)'."""iffileisNone:file=sys.stderrprint_exception(sys.last_type,sys.last_value,sys.last_traceback,limit,file)defprint_stack(f=None,limit=None,file=None):"""Print a stack trace from its invocation point. The optional 'f' argument can be used to specify an alternate stack frame at which to start. The optional 'limit' and 'file' arguments have the same meaning as for print_exception(). """iffisNone:try:raiseZeroDivisionErrorexceptZeroDivisionError:f=sys.exc_info()[2].tb_frame.f_backprint_list(extract_stack(f,limit),file)defformat_stack(f=None,limit=None):"""Shorthand for 'format_list(extract_stack(f, limit))'."""iffisNone:try:raiseZeroDivisionErrorexceptZeroDivisionError:f=sys.exc_info()[2].tb_frame.f_backreturnformat_list(extract_stack(f,limit))defextract_stack(f=None,limit=None):"""Extract the raw traceback from the current stack frame. The return value has the same format as for extract_tb(). The optional 'f' and 'limit' arguments have the same meaning as for print_stack(). Each item in the list is a quadruple (filename, line number, function name, text), and the entries are in order from oldest to newest stack frame. """iffisNone:try:raiseZeroDivisionErrorexceptZeroDivisionError:f=sys.exc_info()[2].tb_frame.f_backiflimitisNone:ifhasattr(sys,'tracebacklimit'):limit=sys.tracebacklimitlist=[]n=0whilefisnotNoneand(limitisNoneorn<limit):lineno=f.f_linenoco=f.f_codefilename=co.co_filenamename=co.co_namelinecache.checkcache(filename)line=linecache.getline(filename,lineno,f.f_globals)ifline:line=line.strip()else:line=Nonelist.append((filename,lineno,name,line))f=f.f_backn=n+1list.reverse()returnlistdeftb_lineno(tb):"""Calculate correct line number of traceback given in tb. Obsolete in 2.3. """returntb.tb_lineno